Plate towers types

Fluidized-Bed Vinegar Reactors. Intimate contact of air A.cetohacter is achieved in fluidized-bed or tower-type systems. Air introduced through perforations in the bottom of each unit suspends the mixture of Hquid and microorganisms within the unit. Air bubbles penetrating the bottom plate keep Jicetobacter m. suspension and active for the ethanol oxidation in the Hquid phase. Addition of a carrier for the bacterial ceUs to the Hquid suspension is reported to improve the performance (58—60). 

FIG. 14-79 Cost of trays in plate towers. Price includes tray deck, bubble caps, risers, downcomers, and structural-steel parts. The stainless steel designated is type 410 Peters and Timmerhaus, Plant Design and Economics for Cbemical Engineers, 4th ed., McGraw-Hill, New York, 1.9.91). 

Plate towers are more subject to plugging and fouling than venturi-type scrubbers that have large passages for gas and liquid. 

PM Impingement-plate tower collection efficiencies range from 50 to 99 percent, depending upon the application. This type of scrubber relies almost exclusively on inertial impaction for PM collection. Therefore, collection efficiency decreases as particle size decreases. Short residence times will also lower scrubber efficiency for small particles. Collection efficiencies for small particles (< 1 fim in aerodynamic diameter) are low for these scrubbers hence, they are not recommended for fine PM control. 

The problems relating to mass transfer may be elucidated out by two clear-cut yet different methods one using the concept of equilibrium stages, and the other built on diffusional rate processes. The selection of a method depends on the type of device in which the operation is performed. Distillation (and sometimes also liquid extraction) are carried out in equipment such as mixer settler trains, diffusion batteries, or plate towers which contain a series of discrete processing units, and problems in these spheres are usually solved by equilibrium-stage calculation. Gas absorption and other operations which are performed in packed towers and similar devices are usually dealt with utilizing the concept of a diffusional process. All mass transfer calculations, however, involve a knowledge of the equilibrium relationships between phases. 

Figure 24.1 Types of tower or column reactors for gas-liquid reactions (a) packed tower, (b) plate tower, (c) spray tower, (d) falling-film tower, (e) bubble column...

Control device vendors estimate that removal efficiencies range from 95 to 99%. For S02 control, removal efficiencies vary from 80 to greater than 99%, depending upon the type of reagent used and the plate tower design. Most current applications have an S02 removal efficiency greater than 90%. 

Plate tower absorbers, 7 27, 28-29 Plate-type separators, 76 644 Platforming, 24 274 25 167... 

The absorption can be performed in different types of unit, for example spray tower, packed bed, plate tower, bubble column, static mixer, and bubble tank. Gas-liquid interfacial area and liquid fraction are criteria for equipment selection. 

The objective of absorption equipment is to provide intimate contact between the liquid concerned and gas, thus facilitating the absorption process. When a large volume of gas is absorbed per unit volume of liquid, a marked rise in temperature may result and devices for the removal of the heat evolved are then an important feature of the equipment. Apart from packed towers, the types of equipment described here include agitated vessels, bubble-plate towers, cooler-absorbers and spray towers. 

The total weight of a dry plate tower is usually less than that of a packed tower designed for the same duty. However, if liquid holdup during operation is taken into account, both types of towers have about the same weight. 

Other Types of Wet Scrubbers. Plate towers, like sieve, valve, and bubble cap towers, and packed beds have been used in the past for dust collection but these are all subject to plugging. 

Filters, heat exchangers, dryers, bubble cap columns, cyclones, etc., are ordinarily designed and built by process equipment manufacturers. However, units of special design for one-of-a-kind operations such as packed or plate towers are quite often designed and built under the supervision of plant engineers. Thus, there is a large variety of this type of equipment, none of it essentially standard. 

Absorption can take place in a countercurrent, cocurrent, or cross-flow device. Vertical countercurrent towers are either built with a metal, plastic, or ceramic packing or constructed as plate towers with various types of plates. This chapter will discuss the solvents used to carry out absorption and the various types of absorption equipment. 

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